(a) Field of the Invention
The present invention relates to a variable steering rack system. More particularly, the present invention relates to a variable steering rack system that has reduced noise when the system is operating.
(b) Description of the Related Art
Generally, a variable steering rack system can regulate a maximum movement displacement of wheels of a vehicle in a case where chains are mounted to tires of the vehicle. FIGS. 1 and 2 shows a steering system including a variable steering rack system according to the prior art. A steering system including a variable steering rack system includes a gear box 10, a steering rack bar 19, a stop knob 17, a case 13, a stopper 15, a motor case 11, a motor 21, a motor gear 22, and an intermediate gear 23. The motor case 11, the stopper 15, and the case 13 are orderly coupled to the gear box 10, and a groove is formed to an interior circumference of the motor case 11. The stopper 15 is disposed to rotate along the groove by the motor 21.
The stop knob 17 is secured to the steering rack bar 19 and in a case that the variable steering rack system is in an initial state, that is, in a case that the variable steering rack system is not operating, the stop knob 17 is formed such that the stop knob 17 is inserted into an interior circumference of the stopper 15. In a case that the variable steering rack system operates, because the stopper 15 rotates corresponding to a movement of the steering rack bar 19, the stop knob 17 is formed such that the stop knob 17 is not inserted into the stopper 15. Therefore, the movement displacement of the steering rack bar 19 is restricted by as much as a thickness of the stopper 15.
The motor 21 transmits a torque to an intermediate gear 23 and the intermediate gear 23 rotates the stopper 15. A stop protrusion 33 is formed in the groove of the interior circumference of the motor case 11 and a knob 31 is formed in the stopper 15. Therefore, as the stopper 15 rotates along the groove in the interior circumference of the case 11, if the stop protrusion 33 contacts to the knob 31 of the stopper 15, the stopper 15 stops rotating. Generally, because the motor 21 utilized in the variable steering rack system rotates at a high speed, a colliding sound is very loud when the stop protrusion 33 contacts with the knob 31 of the stopper 15. In addition, a moving range of the steering rack bar 19 can be controlled or limited by the displacement of the thickness of the stopper 15. In addition, because of the low temperature when the chains are mounted to the tires, in a case that the motor 21 rotates at a low speed in order to prevent the colliding sound, a problem occurs that a performance of the motor 21 is reduced. Furthermore, the layout and shape of the variable steering rack system is complex and complicates the manufacturing process.